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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Thursday, December 13th 2012
Created: Dec 13th 6:55 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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The Bottom Line

Avalanche danger today remains CONSIDERABLE above tree line where the core advisory area received 4-6” of new snow.  Increasing westerly winds overnight have transported this snow into tender wind slabs where it will be likely for a skier to trigger an avalanche.  Below tree line where the surface has generally been unaffected by wind there is a MODERATE danger, primarily for loose snow avalanches.

Also of note: Virtually everywhere else in the region (Front Range, Girdwood, Summit Lake, and Hatcher pass) received more snow than Turnagain pass yesterday so avalanche potential outside of the core advisory area is expected to be higher.


Primary Concern

The modest weight of yesterday’s snow in Turnagain pass (.5” water) probably isn’t enough to affect last Saturdays wind slab on its own.  Add a skier to the equation and you will likely be able to trigger wind slabs on terrain steeper than 35 degrees.  We experienced substantial whumphing at tree line yesterday where the snowpack structure begins to change (weak and unconsolidated below tree line changing to a denser slab or wind scoured above).  This whumphing is a big auditory red flag that if the slope were steep enough (greater than 35 degrees) to slide, it probably would have.  Below tree line we found very little to no wind affected snow.


Secondary Concern

Yesterday’s storm snow appeared to be bonding fairly well to last Saturday’s accumulation.  Snowpit test results below tree line consistently failed at the interface between Saturday’s storm snow and the November facets.  Though a slab is beginning to amalgamate at these lower elevations, my greater concern today is sluffing.  Our snowpack is still very loose in wind protected areas and a skier on steep terrain has the potential to entrain a significant amount of sluff in the form of storm snow and facets.  Just how weak this lower elevation snow is becomes quite obvious as your ski tips continually submarine into the October and November facet layers. 


Mountain Weather

Yesterday's storm roared through south central with a vengence leaving upwards of 15" in favored areas such as Hatcher pass.  Unfortunately Turnagain pass found itself in the "Donut hole" with a meager 4-6" of accumulation.  Overnight winds have picked up from the west and will continue to blow today in the 20-40mph range, tapering this evening.  We can expect a trace amount of snow to fall today over the advisory area as temps look to stay below the freezing mark at all elevations. 

This evening winds will back to the east in advance of a low pressure system building in the gulf.  As this low moves into Prince William Sound tomorrow, the Chugach and Kenai mountains should experience some snowfall Friday, though highest accumulations will likely be east of our area in the Sound.

Storm totals for 12/12/12:

Turnagain pass: 4-6"

Summit Lake: 8"

Anchorage bowl: 5-11"

Girdwood: 8-12"

Hatcher pass: 12-15"


This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas). 

Wendy will issue the next advisory Friday morning, December 14th.

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


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